Firewall in multi-story steel construction
Firewall in multi-story steel construction
(OP)
I am working on a 3-story building with a 2 hour firewall that cuts right through it. The building has concrete over metal deck floors and steel beams and columns. The building is located in a high seismic region and the floor diaphragm needs to be continuous through the wall. My thought was to select a floor thickness with a 2 hour rating so that the 2 hour wall is interrupted by another 2 hour element. The wall would be attached to the deck above and below on both sides with break away clips to satisfy the structural integrity requirements of the IBC. Does that seem like a solution that would satisfy the code requirements and keep the diaphragm intact? Has anyone come up with a different solution? I would love to see a detail if you have one!






RE: Firewall in multi-story steel construction
RE: Firewall in multi-story steel construction
RE: Firewall in multi-story steel construction
In my location they generally don't build firewalls out of double stud walls. At least not that I've seen yet.
RE: Firewall in multi-story steel construction
If masonry, steel columns in a fire situation will expand much more rapidly than masonry and will tend to crack the firewall to such an extent that it no longer acts as a firewall.
Your detail needs to take into account the continuity of the deck and the continuity of the firewall, not a simple requirement.
BA
RE: Firewall in multi-story steel construction
RE: Firewall in multi-story steel construction
Dik
RE: Firewall in multi-story steel construction
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin
RE: Firewall in multi-story steel construction
BA
RE: Firewall in multi-story steel construction
Happily Retired........
RE: Firewall in multi-story steel construction
Dik
RE: Firewall in multi-story steel construction
Dik
RE: Firewall in multi-story steel construction
Don't do fire walls in multi-story construction, particularly in high seismic areas.
If you do have a fire wall in multi-story construction, you really need to have 2 buildings; which means 2 fire walls and a seismic joint between.
RE: Firewall in multi-story steel construction
I am not fully up to date on the requirements in the Canadian code, but I am looking at NBC 2005 User's Guide which has a section entitled "Commentary C - Structural Integrity of Firewalls". This commentary suggests four design approaches as follows:
1. Double Firewall
2. Cantilever Firewall
3. Tied Firewall
4. Weak Link Connections
The double firewall is undoubtedly the best but is expensive.
I have never used the cantilever firewall and as stated earlier, I doubt that it could be economically used on anything but a single story building.
I have used the tied firewall concept on a few occasions. In this approach, the structure on each side provides lateral support to the firewall and the structure is tied together in such a way that lateral forces resulting from the collapse of the structure on one side of the firewall are resisted by the structure on the opposite side. I believe it to be the most practical way to accomplish the desired objective.
I have never used weak link connections and, although approved by our code, I don't trust the system to function properly so I cannot recommend it.
BA
RE: Firewall in multi-story steel construction
The free standing wall was reinforced concrete and the client's choice, it was for a stacker crane warehouse storing extremely volatile and sometimes explosive materials (cans of volatile liquid becoming overheated in the fire and bursting).
On a shopping mall, we put an expansion joint over an exit corridor with combination firewall/shear walls on either side. The steel (cantilevered top chords of the joists) did not connect in the middle but the flooring and roofing expansion joints did.
Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin